Neuronto Agentic Resource Discovery (ARD) Index

Neuronto

The Agentic Resource Discovery index.

One search across every public ARD registry.

neuronto.com · API · Manifest

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What is ARD?

ARD is short for Agentic Resource Discovery, an open specification for how AI agents find the tools, skills, agents and APIs they need, published in June 2026 by a working group including Google, Microsoft, Hugging Face, AWS, Cisco, GitHub, Nvidia, Salesforce and Snowflake.

An agentic resource is anything an AI client can call to get work done: an MCP server, an A2A agent, a skill, an API, a workflow.

ARD answers one question, "what is available for this task?", and then gets out of the way. It is not a runtime and does not replace MCP or A2A. It tells an agent what exists; the agent connects using the resource's own protocol.

The problem it solves

Today an agent can only use capabilities someone installed for it in advance. Every tool has to be wired in by hand, and every tool description has to sit in the context window, competing for space with the actual work. That model does not survive contact with an ecosystem of thousands of tools, let alone millions.

ARD moves the selection problem out of the context window and into a search service, the same shift the early web made when it went from curated link directories to search engines.

For that to work, two sides have to exist. Publishers describe what they offer at a well-known location on their own domain. Registries index those descriptions and answer queries. Neuronto is both.

Why a federated index

The specification defines three federation modes and makes auto the default: a registry queries its peers, merges their results, and returns one set.

In practice each public registry answers only from its own catalogue, so the same question asked in four places returns four different answers and the client has to pick a side. That is the problem Neuronto exists to remove.

Ask Neuronto once and the query fans out across every public ARD registry concurrently. Results are fused with reciprocal rank fusion, which combines the orderings rather than the scores, necessary because each registry calibrates differently, and importing another service's scoring would import its biases with it.

The response says which registries answered and which timed out, so a caller always knows how much of the federation is behind an answer.

What it does differently

Federated by default. federation: auto implemented as specified: concurrent fan-out under a hard time budget, fused ranking, per-upstream reporting. A slow peer costs the budget and nothing more.

Complete conformance. Passes the specification's official conformance tool as both a registry and a publisher with zero errors and zero warnings, including the optional GET /agents listing as a properly paginated object.

Type normalisation. Three media types for MCP servers are in circulation (application/mcp-server, application/mcp-server+json, application/mcp-server-card+json) and two URN prefixes appear as discovery identifiers (urn:air: and urn:ai:). Because filters match exactly, entries get dropped silently. Neuronto normalises both on ingest, so a filter for MCP servers returns them however the publisher spelled the type.

A verified tool index, not just a server index. Every other registry stores a server name and whatever prose its publisher wrote. Neuronto handshakes with each indexed MCP endpoint and reads its tools/list, so the index holds the real tool names and input schemas, the thing an agent actually has to match on. Currently 31,411 verified tools across 2,223 servers, plus 1,918 endpoints recorded as requiring credentials, which no other registry reports. Introspection is read only: a tool is never called.

Hybrid retrieval. Sparse BM25 and dense vectors, fused with the same reciprocal rank fusion used for federation, so one query runs lexical, semantic and federated retrieval and returns a single ordering. The dense leg rides inside the federation budget and contributes nothing if it is unavailable, so the lexical fast path is never slowed by it.

Verified liveness. Indexed endpoints are probed and non-responding ones demoted in ranking. Registries built on self-published manifests accumulate dead links quickly; serving them is the fastest way to become the index nobody trusts. Entries are demoted rather than deleted, because services come back.

Ranking that separates. A relevance score is only useful if the gap between the first and fifth result is legible. Scores are scaled to preserve real separation instead of compressing everything into a narrow band.

Where it fits

• Agent builders, stop hard-coding integrations. Ask for a capability at runtime and connect to whatever currently serves it best.
• API and tool vendors, publish one manifest on your own domain and become discoverable to every ARD client, without applying to a curated marketplace.
• Platform teams, run discovery over internal services so agents inside the organisation find them the same way they find public ones.

Using it

Search this index and the whole federation in one call:

curl -s https://neuronto.com/search \
  -H 'content-type: application/json' \
  -d '{"query":{"text":"scrape a website behind cloudflare"},"federation":"auto"}'

Or install it as an MCP server, so an agent searches from the interface it already speaks:

claude mcp add --transport http neuronto https://neuronto.com/mcp

Registry API

Endpoint	Purpose
POST /search	Ranked results. federation: auto (default), referrals, none.
POST /explore	Facet counts over the index.
GET /agents	Deterministic paginated listing, for browsing rather than ranking.
POST /mcp	The same search as an MCP tool.

No key and no signup. Relevance scores are semantic only and are never a trust, compliance or safety rating, the specification is explicit that trust evaluation is decoupled from discovery.

Searching tools instead of servers

When you already know the shape of the call you need, the server hosting it is an implementation detail:

curl -s 'https://neuronto.com/tools?q=extract+text+from+a+pdf&limit=5'

Every tool returned was read from that server's own tools/list. The same search is available to agents as the MCP tool find_tool, alongside find_resource and registry_stats.

Measuring whether any of this works

GET /bench publishes ARD-Bench, a head to head retrieval measurement across the public ARD registries. Ground truth is the publishers' own representativeQueries, so nothing is hand labelled, and the harness is app/bench.py in this repository.

The response separates two things that are easy to confuse: coverage, whether a registry indexes the target at all, and recall@k_when_carried, whether it retrieves the target when it does hold it. It also states its own known bias, and it reports the results that do not flatter us. In the current run, federated search scores slightly below lexical only and costs far more latency.

Who publishes an ARD manifest

GET /adoption tracks adoption of the specification itself: a named watchlist of organisations, and the manifest rate across every host the crawler has seen. At the time of writing, three of the twenty organisations on the watchlist publish a manifest: Hugging Face, Vercel and Zapier. All three serve it at /.well-known/ai-catalog.json, the path v0.91 renamed. Of 178 publishers our crawler has found, 157 serve the older ai-catalog.json and only 14 serve ard.json, which is why the tracker checks both: measuring the path rather than the practice gets the answer wrong.

The badge

If your MCP server is in the index, a badge states what we verified: how many tools your server returned to tools/list, and whether the endpoint answers.

[![Neuronto verified tools](https://neuronto.com/badge/your.publisher.id.svg)](https://neuronto.com/console?domain=your.publisher.id)

The publisher id is the publisher segment of your URN, or your domain. The badge is a statement about what was observed, never a trust, safety or quality rating. Not indexed yet? Publish a manifest and the crawler will find you, or run the console audit.

Publishing your own resources

Serve a manifest at /.well-known/ard.json on your domain describing what you offer. Neuronto's crawler picks it up; there is no submission form and no allowlist.

Include representativeQueries on every entry. It is the term registries build their semantic index from, and an entry without it is a valid catalogue entry that no search will ever return.

Specification

• Agentic Resource Discovery, v0.91
• ards-project/ard-spec

Licence

Apache-2.0